text: Possibly the most widely encountered
  kind of process in cascade transformations, pericyclic reactions include
  cycloadditions, electrocyclic reactions and sigmatropic rearrangements. Although some of the abovementioned
  instances of nucleophilic/electrophilic and radical cascades involved
  pericyclic processes, this section contains only cascade sequences that are
  solely composed of pericyclic reactions or in which such a reaction arguably
  constitutes the key step.
  A representative example of a pericyclic cascade is the endiandric acid cascade
  reported by Nicolaou et al. in 1982 (Scheme 8). Herein the highly unsaturated system 39 was first hydrogenated to the
  conjugated tetraene species 40,
  which upon heating underwent an 8π-conrotatory
  electrocyclic ring closure, yielding cyclic intermediate 41. A second spontaneous electrocyclization, this time a
  6π-disrotatory ring closure, converted 41
  to the bicyclic species 42, the
  geometry and stereochemistry of which favored a subsequent intramolecular
  Diels-Alder reaction. The methyl ester of endiandric acid B (43) was thus obtained in 23% overall
  yield.
  A pericyclic sequence involving intramolecular
  hetero-cycloaddition reactions was employed in the total synthesis of naturally
  occurring alkaloid (–)-vindorosine (Scheme 9). Rapid access to the
  target was achieved from a solution of 1,3,4-oxadiazole 44 in triisopropyl benzene subjected to high temperatures and
  reduced pressure. First an inverse-electron-demand hetero-Diels-Alder reaction
  occurred to give intermediate 45.
  Thermodynamically favorable loss of nitrogen generated the
  1,3-dipole-containing species 46. A
  spontaneous intramolecular [3+2] cycloaddition of the 1,3-dipole and the indole
  system then formed the endo-product 47 in 78% overall yield. Further
  elaboration yielded the target natural product 48.   
  The total synthesis of (–)-colombiasin A reported in 2005
  by the Harrowven group included an electrocyclic cascade (Scheme 10). When subjected to heat via microwave
  irradiation, squarate derivative 49
  underwent an electrocyclic opening of the cyclobutene ring, followed by a
  6π-electrocyclic ring closure that yielded bicyclic intermediate 51. Tautomerization thereof gave the
  aromatic species 52, which upon
  exposure to air was oxidized to product 53
  in 80% overall yield. The target (–)-colombiasin A (54) was then obtained from 53
  via a heat-facilitated Diels-Alder reaction
  followed by cleavage of the tert-butyl
  protecting group.
  Certain [2,2]paracyclophanes can also be obtained via
  pericyclic cascades, as reported by the Hopf group in 1981 (Scheme 11). In this sequence, a Diels-Alder
  reaction between 1,2,4,5-hexatetraene 55
  and dienophile 56 first formed the highly reactive
  intermediate 57, which subsequently dimerized
  to yield [2,2]paracyclophane 58.